Modern medical imaging systems such as magnetic resonance systems, computed tomography systems, PET or SPECT systems, ultrasound installations, etc. are currently able to supply very large amounts of high-resolution image data. A challenge for improving the application of such imaging systems and the results obtained thereby therefore also lies in processing the large amount of measured image data and outputting the latter for a diagnosis and/or intervention planning such that the diagnosing person or planner can identify all relevant information. For this, the three-dimensional image data, which can be measured e.g. in the form of individual slices or else as volume data, is increasingly output in the form of three-dimensional visualizations, referred to as “volume-viewing images” hereinbelow, for example using the so-called “volume-rendering method”. Such an output in the form of volume-viewing images simplifies the interpretation for the diagnosing person, particularly when diagnosing vessels and for intervention planning based thereon, because the observer intuitively obtains a spatial awareness of the illustrated structures and does not solely depend on their own spatial sense like in the interpretation of purely two-dimensional slice images.
In clinical routines, such volume-viewing images of a particular structure, e.g. of one or more particular organs, are these days generally displayed in a standard view that is precisely defined in advance and independent of the available data. That is to say one or more volume-viewing images with different viewpoints (the locations of the virtual “camera”) are generated by default. The visibility of the structures of interest is controlled, inter alia, by the selection of the so-called “transfer function”, which is a measure for how transparent a certain structure is and whether another structure situated therebehind can also be viewed through this structure in the illustration. In addition to transparency, the transfer function can also define the color with which each image voxel in the volume display should be visualized. However, the transfer function is substantially only based on image intensities in this case. This leads to structures with the same image intensity not being displayed independently of one another.
Therefore, in practice, structures determined manually, more particularly organs, are usually freed for a given clinical question in most cases by a specially-trained technical operator. By way of example, this can be brought about with the aid of so-called “punch tools”, which punch out a certain region from the image data in a virtual fashion and so a view of structures situated therebehind is made possible. In the process, volume-viewing images are also generated at the same time as so-called “screenshots” from different expedient or information-rich “camera positions”. These screenshots are generally sent to a radiologist for diagnosis via a suitable image-data network, for example a picture archive and communication system (PACS). The freeing of organs with the aid of punch tools in particular is relatively time-consuming because the operator often has to load up different viewpoints and must form a suitably-shaped punch tool in each viewpoint such that the view of an organ of interest situated therebehind is cleared, for example by removing organs situated closer to the viewpoint. If it then turns out that the view of the actual target organ of interest is not good enough, the operator has to load up a new viewpoint and there has to again free the region in front of the target organ using a suitably adapted punch tool.